This invention relates to the arts of powder metallurgy and microwave heating.
Certain metals may be strengthened by adding to them relatively small quantities of particular materials in such a manner that the added materials do not mix with the metal to form a homogenous phase, but are uniformly dispersed in particulate form throughout the metal. The material which is added may be referred to as a dispersoid, while the metal it is dispersed in is referred to as the matrix metal; the combination is known as dispersion-strengthened metal. Oxides make good dispersoids because of their high hardness, stability at high temperatures, insolubility in matrix metals, and availability in fine particulate form.
The present invention was made in connection with the development of dispersion strengthened copper, where the dispersed particles are of copper oxide or copper having a coating of copper oxide. A unique aspect of strengthening copper by means of a dispersed phase, in contrast with the conventional methods of solid solution hardening or precipitation hardening, is that a significant increase in strength is available while retaining a substantially pure metal matrix with very little or virtually no alloying element remaining in solid solution. This has the advantage of giving markedly higher strength without significant loss in electrical or thermal conductivity or in corrosion resistance.
Copper which is dispersion-strengthened with aluminum oxide is commercially available. Prior to the present invention, the use of copper oxide as a dispersoid in copper was unknown.
Additional information may be found in "Dispersion-Strengthened Materials," 7 Powder Metallurgy, 9th Ed., Metals Handbook, American Society for Metals, 710-727 (1984).